On the face of it, writing about the global trends survey by the United Nations refugee agency (UNHCR) should have been a straightforward reporting job.

The statistics, published on 19 June 2013, show that by the end of 2012, 45.2 million people worldwide were considered as forcibly displaced, which includes 15.4 million refugees.

A story about the figures was published online the same day. More of the statistics were used as part of a Guardian Datablog post, and a page was given over to the story, with graphics, in the following day's newspaper.

However, a reader believed that there was one important statistic missing from the datablog. He wrote: "You completely failed to quote the number of Palestinian refugees, citing instead that the largest number of refugees, by country of origin, is from Afghanistan, at 2,585,600. What you omitted, presumably by choice, is the information from the same UN report [actually it was only in the accompanying press release] that the article is based on, as follows: 'Of 10.5 million refugees under UNHCR's mandate … a further 4.9 million Palestinian refugees fall under the mandate of its sister-agency, the UN Relief and Works Agency.'

"I am curious as to why your article completely omits to mention the Palestinian refugees. Surely, as the largest group of refugees in the world, they should merit some mention. Indeed, they should be at the head of the bar graph."

The reader has a theory as to why the Palestinians had been "disappeared".

"Perhaps mentioning the Palestinian refugees might raise in people's minds the question as to how it was that almost 5 million people and their descendants … became refugees."

Notwithstanding the best efforts of the datablog's author and colleagues, the reader became convinced that the omission was wilful. The correspondence was referred to the readers' editor.

According to the UNRWA website this is because: "As UNRWA was set up in 1949, Palestine refugees were specifically and intentionally excluded from the international refugee law regime established in 1951. The 1951 Convention relating to the Status of Refugees and the 1967 Protocol thereto exclude Palestine refugees as long as they receive assistance from UNRWA. The UN Office of the High Commissioner for Refugees (UNHCR) provides assistance and protection to Palestine refugees outside UNRWA's areas of operations."

There are brief references in a footnote and the text of the report to explain that historical position. The 4.9 million Palestinians are counted in the report as part of the total of 15.4 million refugees. But they don't feature in the bar charts the Guardian reproduced from the UNHCR report; that's why Afghanistan tops the chart.

The only Palestinian refugees who do appear in the UNHCR statistics are 94,804 who are in countries where UNRWA doesn't operate, and thus fall under the protection of the refugee agency.

The Guardian should have made things clearer, particularly in the newspaper story, where there is more of an impression that these are overall refugee figures.

Both stories were footnoted to deal with another unrelated error and a reference to the bulk of Palestinian refugees. The following correction was published: "A story about the latest figures from the UN's refugee agency (UNHCR) for people uprooted from their homes, wrongly stated that '45.2 million were displaced last year'. In fact, that is the figure for all currently displaced people (Refugee crisis, 20 June, page 26). An online Datablog post (19 June) setting out the full data in the report made the same mistake in a subheading, 'More than 45.1 million people were displaced last year'. A reader has pointed out that 4.9 million Palestinian refugees don't appear in the statistics in our stories: that is because they are not registered with the UNHCR but with the United Nations Relief and Works Agency for Palestine Refugees in the Near East. They are recorded in a footnote to the report as being part of the total of 15.4 million refugees, one of the key components of the 45.2 million."